1. Field of the Invention
The present invention relates to electrical lock thawing devices, and more particularly pertains to an electrical lock thawing device of the type having an electrically heated elongated blade dimensioned for insertion into the key slot of a frozen lock cylinder.
2. Description of the Prior Art
Various types of electrical lock thawing devices are known in the prior art. A typical example of such an electrical lock thawing device is to be found in U.S. Pat. No. 3,022,408, which issued to R. Wagner on Feb. 20, 1962. This patent discloses an electrically heated key for unlocking a frozen lock which utilizes an electrical resistance heating element. U.S. Pat. No. 3,450,859, which issued to H. Brucker on Jun. 17, 1969, discloses a device for heating keys for defrosting frozen lock cylinders. The device includes a housing having an opening at one end and a carriage having clamping means for engagement with the head of a key. The housing includes a gas burner which is started and ignited by the movement of the carriage to extend the shank portion of a key. An alternative electrically heated embodiment is shown in FIGS. 8 and 9 and described in column 4, line 52 through column 51, line 12. U.S. Pat. No. 3,973,422, which issued to F. Cervera on Aug. 10, 1976, discloses a key case which includes a battery and a coil disposed in coaxial relationship with respect to a swivel pin for carrying keys. A switch selectively connects the battery and the coil for heating of the keys to assist in thawing frozen locks. U.S. Pat. No. 4,247,753, which issued to N. Jaronen on Jan. 27, 1981, discloses a battery operated portable thawing device for frozen locks which has an electrically heated thawing stick sized for insertion into a lock key hole. U.S. Pat. No. 4,303,825, which issued to N. Jaronen on Dec. 1, 1981, discloses a lock thawing device which utilizes an electrical resistance heating wire dimensioned for insertion into a lock key slot.
While the above mentioned devices are directed to electrical lock thawing devices, none of these devices utilizes a housing having a rechargeable battery and a plug mounted for movement between retracted and extended positions for engagement with a conventional AC in conjunction with the use of a removable heating blade retained by a spring ball detent. Inasmuch as the art is relatively crowded with respect to these various types of electrical lock thawing devices, it can be appreciated that there is a continuing need for and interest in improvements to such electrical lock thawing devices, and in this respect, the present invention addresses this need and interest.